Cold-pressed refractory materials

ABSTRACT

Cold-pressed refractory bodies are impregnated with vapors of silicon or transition metals to give improved strength and impact resistance without sintering.

United States Patent Brown Nov. 25, 1975 1 COLD-PRESSED REFRACTORY [56] References Cited MATERIALS UNlTED STATES PATENTS [75] Inventor: Clifford Gordon Brown, Fetcham, 3,065,108 11/1962 Seelig et a1. 1. 117/107 England 3,356,618 12/1967 DidCOt et 61...... 117/106 A x 3,366,464 1 1968 0 11 1. 117 106 R x Assigneel United States Borax & Chemical 3,544,348 12/1970 13:62:: 117 71 x Corporation, L05 Angeles, Calif. 3,622,402 11 /1971 Baranow et al. 117/107.2 P x 3,708,325 1/1973 Kurtz et al. 117 107.2 R x [221 1973 3,718,441 -2/1973 Landingham 1 17 107 x [21] Appl. No.: 420,329

Related U.S. Application Data Continuation-impart of Ser. No. 263,967, June 19, 1972, abandoned.

Foreign Application Priority Data July 1, 1971 United Kingdom 30844/71 Primary Examiner-Harris A. Pitlick Attorney, Agent, or Firm-James R. Thornton ABSTRACT strength and impact resistance without sintering.

4 Claims, No Drawings COLD-PRESSED REFRACTORY MATERIALS -continued Chromium l550 l700C. (preferably about l600C.) This 1s a continuatlon-mpart of my copendmg appllon Moon 500C (preferably abom [49006) catlOIl, Ser. No. 263,967 filed June 19, 1972 and now Cobalt 1390- 1490c. (preferably about 14s0c. abandoned. The invention relates to the production of N'ckel (Preferably 440ml hard shaped bodies made from boron-containing compounds, in particular from refractory metal borides and In the practice of this invention, the boron-containfrom boron-carbon compounds, such as boron carbide. ing body, eg in the form of a pellet about inch in The usual method of processing refractory materials length and about V2 inch in diameter, is placed in a cruto form hard shaped bodies is that of hot-pressing, cible made of graphite or other suitable material which is a comparatively expensive process. An altermounted on atungsten support, together with sufficient native process of cold-pressing followed by sintering infiltrating or impregnating agent to fill the crucible may also be employed for certain powdered refractory loosely. A diluent, such as silicon carbide, may be materials. added to the contents of the crucible, if desired. The It is an object of this invention to provide shaped whole is surrounded by a silica envelope with suitable bodies of boron-containing refractory materials of high arrangements for the required ranges of temperature strength and impact resistance by a method which does and pressure to be maintained. The shaped body and not require hot-pressing or sintering. Such bodies may infiltrating agent can be heated by means of a 5 kilobe used in place of hot-pressed articles, such as tool watt R.F. coil for about 80 minutes (preferably 50 tips, shot-blast nozzles, ceramic armour, or in wear- 20 70 minutes) at the appropriate temperature. During resistant applications such as bearing surfaces. the process an inert atmosphere, such as argon, is main- It has now been found that porous, non-sintered bodtained. ies of boron-carbon compounds and bodies of boron- Suitable conditions for this invention are shown in metal compounds can be impregnated with silicon or Examples 1 10 of Table l, which describes amounts with a transition metal by vacuum deposition of a vapor 5- of refractory boride and of infiltrating agent, times of of the chosen element. The porous bodies are coldheating, and temperatures and pressures used.

TABLE I Exam- Refraclnfiltrant Tempera- Time Pressure ple tory ture (min.) (mm. Hg.) No. (g.) (g.)

1 TiB,(3.0 Si (5.0g) 1340-1350 60 6 7.5 2 138343.09 51 (5.0 1330-1370 60 7.0 3 LaB (4.0g) Mn (20g) ll80-ll90 60 4.5-10 4 W8 (8.0g) Mn (205) 1155-1 I80 60 S 8 5 ZrB,(4.0g) Cr (20g) l580-l600 60 6.5-8 6 TiB,(3.0 Cr (20g) [580-1600 60 60-70 7 B.c (2.0g) Mn (20g) 1140-1230 60 60-90 8 TiB=(3.0g) Fe (20g) 1460-1490 60 6.5-7.5 9 W8 (8.0g) Co (20g) 1430-1480 60 6.0-8.0 10 ZrB (4.0g) Ni (20g) 1420-1445 60 7.0-8.5

pressed bodies of boron carbide or boron-metal com- All the above reactions were carried out in an atmopounds of metals of Groups IIA, IIIA, IVA, VA, or VIA sphere of argon.

of the Periodic Table, especially the metal borides. The All products were found to have low residual porosimpregnation process results in bodies of high strength ity, high hardness, and a metallic lustre when polished. and impact resistance without need for sintering after The infiltration produced little or no change in the diimpregnation. mensions of the refractory body, but substantially im- The preferred impregnants used for the vacuum improved the properties thereof. Such products are dispregnation are silicon, iron, cobalt, nickel, manganese tinctly different from shaped bodies which have been and chromium. The impregnation is effected by heating coated in a pack, such as by diffusion coating which rethe silicon or metal, such as in a pack, under reduced sults in only slight diffusion into the surface of the artipressure, such as 4-]0 mm. Hg, preferably about 6-8 cle coated. mm. Hg, to a temperature below the melting point at Results in terms of increase in density are shown in atmospheric pressure of the silicon or metal, which is Table II for some typical combinations of boron-consufficient to volatalize the element. The porous borontaining body impregnant. containing body is held in the vapors of the element TABLE 11 thereby impregnating the body throughout with the ele- Density of ment and thereby strengthenmg and harden ng the Starting Starting Density of body. Thus, there is a gaseous m1grat1on of the impregrm in m m Materi i Product nating material throughout the interconnecting pores (gm of the porous body followed by reaction and/or con- BC Mn 537 th i l TiB Si 3.15 3.45 densation, depending on e impregn mg Mn 3J5 4-H ed- Tia, Cr 3.15 3.64 The temperatures normally employed in the practice MoB, M n 5.00 5.40 fth' f th l'nfltratin 0r im re 0 1s mvention or e severa 1 1 g p g 2TB Mn 415 506 nating agents are as follows: ZI'B; Cr 4.25 6.01 LaB 51 1.83 3.86 Baa, Si 3.12 3.44

(preferably about 1200"C.) (preferably about l340C.)

Manganese Silicon *assuming 30% porosity The impregnated shaped bodies can be machined, eg with a diamond saw, to shape appropriate to a desired end use.

Various changes and modifications of the invention can be made and, to the extent that such variations incorporate the spirit of this invention, they are intended to be included within the scope of the appended claims.

What is claimed is:

l. A cold-pressed, non-sintered boron-containing refractory body which is impregnated throughout with a material selected from the group consisting of manganese, silicon, chromium, iron, cobalt, and nickel, said impregnated body having a low residual porosity and increased density and hardness, wherein said boron- 4 containing refractory is selected from the group consisting of boron-metal compounds of metals of Groups "A, lIlA, IVA, VA, and VIA of the Periodic Table.

2. An impregnated cold-pressed body according to claim 1 in which said boron-containing refractory is zirconium diboride.

3. An impregnated cold-pressed body according to claim 1 in which said boron-containing refractory is titanium diboride.

4. A cold-pressed, non-sintered boron carbide body impregnated throughout with silicon, thereby having a low residual porosity and increased density and hardness. 

1. A COLD-PRESSED, NON-SINTERED BORON-CONTAINING REFRACTORY BODY WHICH IS IMPREGNATED THROUGHOUT WITH A MATERIAL SELECTED FROM THE GROUP CONSISTING OF MANGANESE, SILICON, CHROMIUM, IRON, COBALT, AND NICKEL, SAID IMPREGNATED BODY HAVING A LOW RESIDUAL POROSITY AND INCREASED DENSITY AND HARDNESS, WHEREIN SAID BORON-CONTAINING REFRACTORY IS SELECTED FROM THE GROUP CONSISTING OF BORON-METAL COMPUNDS OF METALS OF GROUPS IIA, IIIA, IVA, VA, AND VIA OF THE PERIODIC TABLE.
 2. An impregnated cold-pressed body according to claim 1 in which said boron-containing refractory is zirconium diboride.
 3. An impregnated cold-pressed body according to claim 1 in which said boron-containing refractory is titanium diboride.
 4. A cold-pressed, non-sintered boron carbide body impregnated throughout with silicon, thereby having a low residual porosity and increased density and hardness. 